Astronomical Technology and the Exploration of the Universe. Prof André Buys

Transcription

1 Astronomical Technology and the Exploration of the Universe Prof André Buys 1

2 Naked eye astronomy Naked Eye Astronomy The angular resolution of the naked eye is about 1 (one arcminute). The naked eye can see: about 1,500 stars in a dark sky (6th magnitude). colours only in bright stars and the planets. The eye uses rods instead of cones at low light levels. some star clusters: Pleiades, h/χ Persei, M13 and the Orion Nebula. two true galaxies: Andromeda (M31) and Triangulum (M33). five planets: Mercury, Venus, Mars, Jupiter, and Saturn. 2

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4 The Namaqua legend of the daughters of the sky god. Tycho Brahe ( ) The zenith of nakedeye astronomy His planetary observations were consistently accurate to within about 1'. His stellar observations were even more accurate, varying from 32" to 49" for different instruments. His records enabled Kepler to discover the laws of planetary motion, which provided evidence for the Copernican heliocentric theory of the solar system. 4

5 The dawn of astronomical technology The optical telescope Galileo Galilei ( ) Galileo is generally recognised as the inventor of the astronomical telescope. 5

6 Galileo s telescopes (1610) In the Museum of the History of Science in Florence Istituto e Museo di Storia della Scienza Objective diameter: 51 mm Focal length: 1,330 mm Magnification: 14 Field of view: 15' Istituto e Museo di Storia della Scienza Objective diameter: 37 mm Focal length: 980 mm Magnification: 21 Field of view: 15' Galileo s publishes his astronomical discoveries Galileo published Sidereus Nuncius (Starry Messenger) in March In this work he announced the discovery of Jupiter's moons and other observations. 6

7 Galileo s observations Moon Phases of Venus Jupiter s moons Saturn s rings Atalay s proposition On page 59(b) of Leonardo s Codex Atlanticus appears this drawing. Bülent Atalay proposed in 2005 that it is Leonardo s telescope. The page also contains a study of light reflection of a concave mirror. 7

8 Optical design of Leonardo s telescope Mirror: Spherical concave speculum metal Mirror diameter: 100 mm Focal length: 500 mm Focal ratio: f5 Eyepiece: Bi-convex glass (Handheld magnifying glass ) Eyepiece diameter: 25 mm Focal length: 15 mm Magnification: 33x Replica of Leonardo da Vinci s telescope 8

9 Leonardo s long focal-length sperical mirror grinding machine Leonardo s drawing Working model The quality of the optics determines what you see! The moon Leonardo da Vinci saw in 1513 through his reflecting telescope. The moon Galileo Galilei saw in 1609 through his refracting telescope. The moon we see today through a modern amateur telescope. 9

10 We draw what we see Leonardo da Vinci Galileo Galilei Modern moon map Aperture fever Max. Mirror Diameter (meters) Galileo Robert Hooke William Herschel Lord Rosse's Leviathan Birr Castle, Ireland Hooker 100-inch reflector Mt Wilson Hale 200-inch reflector Palomar Mountain Keck 1 & 2 Mauna Kea, Hawaii

11 2x 8.4 meter Large Binocular Telescope 2 x 8.4 m Large Binocular Telescope, Mt Graham, Arizona, USA 2x 10 meter Keck Telescopes, Mauna Kea, Hawaii 11

12 Discovery of the expansion of the universe In 1908 Henrietta Swan Leavitt discovered the Cepheid variable stars - a standard candle for cosmic distance measurements. In 1912 Vesto Slipher observed the shift of spectral lines of galaxies (galactic redshifts) In the 1930's, Edwin Hubble discovered the relationship between the rate that galaxies were receding and their distances from us. Hubble s Law The 100 inch Hooker telescope at Mount Wilson Observatory that Hubble used to measure galaxy redshifts and the rate of expansion of the universe. 12

13 Limitations on the resolution of telescopes Chromatic Aberration Geometrical Aberration Air Turbulence (Seeing) Aberration Diffraction Aberration Adaptive optics Artificial guide stars formed by resonance fluorescence emission of laser light from the mesospheric sodium layer (90 km high) in the atmosphere. 13

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17 Expanding our vision Exploring across the electromagnetic spectrum 17

18 The 0.85-meter Spitzer Infrared Space Telescope launched in August

19 Radio Astronomy In 1932 Karl Jansky, an engineer with Bell Telephone Laboratories, discovered a strong source of radio static originating from the central region of our galaxy In 1937 Grote Reber, constructed a fully steerable large parabolic dish radio telescope (9m in diameter). He used it to construct a sky map of radio signals. In 1946 Martin Ryle and Joseph Lade Pawsey development radio interferometry. This creates a combined telescope that is the size of the antennas furthest apart in the array. Jansky s Reber's rotating original 20.7 dish Mhz antenna. antenna 19

20 Radio Astronomy Radio astronomy has led to the discovery of several classes of new objects such as pulsars, quasars and radio galaxies. Radio astronomy is also partly responsible for the discovery of dark matter; radio measurements of the rotation of galaxies suggest that there is much more mass in galaxies than has been directly observed. Pulsar at the center of the Crab Nebula (Chandra X-Ray Observatory) The Chandra X-ray Observatory The Chandra X-ray Observatory launched in July

21 A dramatic new Chandra image of the nearby galaxy Centaurus A provides one of the best views to date of the effects of an active supermassive black hole. Opposing jets of high-energy particles can be seen extending to the outer reaches of the galaxy, and numerous smaller black holes in binary star systems are also visible. Southern Africa s contribution 21

22 South Africa s Radio Astronomy Reserve 22

23 Southern African Large Telescope (SALT) The SALT telescope currently has the largest mirror in the world (11 meters diameter). 23

24 SALT s instruments The SALT imaging and acquisition camera (SALTICAM) The Robert Stobie Spectrograph (RSS) SALT High Resolution Spectrograph (SALT-HRS) Earth Observer's view of a polar at the start (left) and end (right) of eclipse. The artist Bob Watson's painting of a 'Polar' binary. Sequence of brightness measurements of the polar. 24

25 The Bird (IRAS ) three-galaxy collision about 650 million light years away as imaged by European Southern Observatory's Very Large Telescope (VLT) in Chile. Scientists at SALT analysed light from different parts of the Bird using the Robert Stobie Spectrograph to show in detail how they were moving. Hartebeesthoek Radio Astronomy Observatory The 26-m Hartebeesthoek Radio Telescope 25

26 The Very Long Baseline Interferometry (VLBI) Technique a Radio Telescope the size of the Earth HartRAO co-operates with radio telescopes on other continents and in space to form a virtual telescope the size of the Earth - or even larger using the orbiting radio telescope HALCA. VLBI lets us see details much smaller than can be seen with the best optical telescopes. VLBI is used, for example, to map masers around stars in the Milky Way and the jets in quasars. Square Kilometre Array 26

27 Australia and Southern Africa short-listed for SKA location Proposals for siting the SKA were received from Argentina/Brazil, Australia, China and Southern Africa on 31 December The International SKA Site Advisory Committee decided that the short-list of acceptable sites for the SKA will comprise Australia and Southern Africa. Additional studies of the characteristics of the shortlisted sites will be carried out in 2007 and A final decision of the location of the SKA is expected thereafter. The central region of the the Square Kilometre Array. At its heart lies a phased array capable of observing the whole sky and able to provide multiple beams so that several tasks can be carried out simultaneously. Surrounding this is the compact array of small dishes within a larger, more open, array. 27

28 The Outer Stations of the Square Kilometre Array A view of some of the outer stations of the SKA. These will be arranged in a log-spiral pattern extending out to distances of up to 3,000 km. Those shown are relatively close together as they lie near the central compact region. At greater distances from the centre the spacing between the outer stations increases. MeerKAT prototype dish at HartRAO. 28

29 H.E.S.S. High Energy Stereoscopic System High-energy gamma-ray stereoscopic telescope system located near the Gamsberg, Namibia, consisting of an an array of imaging atmospheric cherenkov telescopes. The future of astronomical technology 29

30 James Webb Space Telescope The James Webb Space Telescope (JWST) is a 6.5 meters infraredoptimized space telescope, scheduled for launch in meter GIANT The 24.5 MAGELLAN meters Giant TELESCOPE Magellan Telescope x sharper images than Hubble 30

31 The Thirty Meter Telescope 42 meter EUROPEAN EXTREMELY LARGE TELESCOPE The 42m European Extremely Large Telescope 31

32 100 meter OWL (Overwhelmingly Large) Telescope 32